1. Field of the Invention
The present invention relates to a device for carrying out an electric connection between two relatively rotatable members via a cable.
2. Description of the Related Art
Various structures have so far been proposed with respect to a relaying device for carrying out an electric connection between two relatively rotatable members via a cable.
As an example of this kind of relaying device between relatively rotatable members, there is one that is structured to include a rotary unit (hereinafter to be referred to as a first rotary unit) having an inside cylindrical section and a fixed unit (hereinafter to be referred to as a second rotary unit) that surrounds the inside cylindrical section of this rotary unit so that the first rotary unit makes a relative rotation, and the rotary unit side and the fixed unit side are electrically connected via a flexible flat cable (hereinafter to be referred to as a cable).
In the above structure, there are cases where the first rotary unit has a disc-shaped upper cover, provided at one end of the inside cylindrical section, that extends outwards in its radial direction. In this case, the cable is bent on one end and is drawn to the outside through a hole provided on the upper cover, and each conductor of the cable is connected to a suitable terminal.
Further, there has also been proposed a structure in which a bus bar is connected to each conductor at one end of the cable and a terminal is connected to the bus bar. In this case, the area surrounding the bus bar may be filled with a resin.
In the above-described relaying device between relatively rotatable members, when the number of circuits increases and the width of the cable correspondingly increases, the following problems occur:
First, since the width of the cable itself is large, it becomes extremely difficult to bend the cable.
Second, when the bus bar is used, for example, since the width of the cable is large, a connection section connected to the upper cover of the first rotary unit must also have a large width, and it becomes difficult to draw the cable to the outside through the hole in the first rotary unit, especially because the upper cover typically has an R-shaped hole, since the upper cover is disc-shaped. In such a situation, there are cases where the bus bar itself is required to have a very complex shape, for example, an R-shape, along the hole.
Further, when the bus bar is used as described above, since the width of the cable itself is large, the connector is also required to have a large width, which makes it difficult to lay out the connector in the upper cover. In this case, the problems of the layout may be addressed if the connector has a two-row terminal, for example. However, the bus bar is then required to have a very complex shape in order to have such a two-row layout.